diff --git a/devtools/startup/DevToolsStartup.sys.mjs b/devtools/startup/DevToolsStartup.sys.mjs
index 50fd07c1365ad25dc31c806f11751368f0d27a46..e26e90ece2d5dc42312f95661b5a38eec3556986 100644
--- a/devtools/startup/DevToolsStartup.sys.mjs
+++ b/devtools/startup/DevToolsStartup.sys.mjs
@@ -829,6 +829,7 @@ DevToolsStartup.prototype = {
     // account (see bug 832984).
     const mainKeyset = doc.getElementById("mainKeyset");
     mainKeyset.parentNode.insertBefore(keyset, mainKeyset);
+    window.dispatchEvent(new window.Event("zen-devtools-keyset-added"));
   },
 
   /**